MONDAY, July 12 (HealthDay News) -- Weight loss might help middle-aged women who are overweight or obese reduce bothersome hot flashes accompanying menopause, according to a new study.

"We've known for some time that obesity affects hot flashes, but we didn't know if losing weight would have any effect," said Dr. Alison Huang, the study's author. "Now there is good evidence losing weight can reduce hot flashes."

Study participants were part of an intensive lifestyle-intervention program designed to help them lose between 7 percent and 9 percent of their weight.

Huang, assistant professor of obstetrics and gynecology at the University of California, San Francisco, said the findings could provide women with another reason to take control of their weight. "The message here is that there is something you can do about it (hot flashes)," said Huang.

About one third of women experience hot flashes for five years or more past menopause, "disrupting sleep, interfering with work and leisure activities, and exacerbating anxiety and depression," according to the study.

The women in the study group met with experts in nutrition, exercise and behavior weekly for an hour and were encouraged to exercise at least 200 minutes a week and reduce caloric intake to 1,200-1,500 calories per day. They also got help planning menus and choosing what kinds of foods to eat.

Women in a control group received monthly group education classes for the first four months.

Participants, including those in the control group, were asked to respond to a survey at the beginning of the study and six months later to describe how bothersome hot flashes were for them in the past month on a five-point scale with answers ranging from "not at all" to "extremely."

They were also asked about their daily exercise, caloric intake, and mental and physical functioning using instruments widely accepted in the medical field, said Huang. No correlation was found between any of these and a reduction in hot flashes, but "reduction in weight, body mass index (BMI), and abdominal circumference were each associated with improvements" in reducing hot flashes, according to the study, published in the July 12 issue of Archives of Internal Medicine.

Huang said that caloric intake and exercise were measured by the participants, who were not always accurate, but "weight can be measured by stepping on scale," so weight loss is a "more accurate measure" of what happened.

About 340 study participants, at least 30 years old, were recruited from a larger study of overweight and obese middle-aged women suffering from incontinence. They were not told the study was examining the effect of weight loss on hot flashes.

At the study's start, about half of both the study and control groups reported having hot flashes; about half of these were at least moderately bothered, and 8.4 percent were extremely bothered.

By six months, 49 percent in the study group, compared with 41 percent in the control group, reported improvement by "at least one category of bothersomeness."

That might not seem like a big difference. But Huang added that, "although 41 percent of women in the control group experienced improvement in hot flashes, quite of few of them experienced improvement by only one category of 'bothersomeness' (as opposed to two categories). Also, of those women in the control group who did not experience improvement, relatively more of them experienced actual worsening of hot flashes (as opposed to no change)."

Dr. Elizabeth Poynor, an obstetrician-gynecologist affiliated with Lenox Hill Hospital, said the study findings are "good news."

"I think this study provides a ground work to look at it (hot flashes) in larger, more detailed and comprehensive studies," said Poynor. "It's very promising," she added.

Poynor said the study provides an impetus to women who need to lose weight for other health reasons, such as diabetes or heart disease, because it can reduce problems like sleep disturbance that can lead to problems with concentration and poor functioning in general.

"It can really help to have a very significant altered quality of life," said Poynor, noting that the physiology of hot flashes, "at least in part a vascular event," is poorly understood and needs more study.

"However, this study provides women and their health care professionals who care for them another intervention to help with bothersome hot flashes in women who are overweight."

More information

The U.S. National Women's Health Information Center has more on menopause.